How to parse JSON into existential type

How to parse JSON into existential type

Hello List!

In some of my JSONs I have part "list of any values", for example:

[1, "hi", "false", 2.71]

To parse it I create type like:

data RespItem = forall a. FromJSON a => RespItem {
riItem :: [a] }

,-------------------------------------------------------------------
| btw, I try `(FromJSON a, Show a, Generic a) => ...` also but don't
| see any difference, so I'm not sure what is right constraints list.
`-------------------------------------------------------------------

And GHC does not allow to derive automatically with "deriving" Show
and Generic instances for existential types, as I see. So I write:

Re: How to parse JSON into existential type

Rather than having an existential, which is difficult to work with at
the best of times, how about making RespItem into something concrete?
You could make your own data type to represent strings and arrays and
objects, etc, but you could also just use Value from aeson, since it
already exists and already has a FromJSON instance.